Cellulose is a complex carbohydrate consisting of thousands of glucose units in a linear chain structure. This polysaccharide is pack into fibers. Hemicelluloses, such as xylans, uronic acid and arabinose are complex carbohydrates that, with other carbohydrates (e.g., pectins), surround the cellulose fibers of plant cells.
Those valuable materials, as other fibrous materials, are currently consisted as a significant ingredient of urban sewage sludge. Reference is made to table 1, presenting cellulose and hemicellulose content, as was sampled and analyzed (triplet test) in Israeli municipal sludge before processing. Crude sludge comprising about 11% (dry weight) cellulose fibers and 14% hemicellulose, wherein dry dense sludge comprising 10% hemicellulose and 2% cellulose. Before digestion the dry dense sludge comprising similar contents. Screening crude sludge by a means of 50 mesh comprising almost equal content of hemicellulose and cellulose (i.e., about 7%). By screening the same in a 130 mesh screens, 12% hemicellulose and 15% cellulose content is obtained.
The sources of sewage fibers are selected from toilet paper; non-digest fruit and vegetable fibers (i.e., new fibers); and cotton, synthetic fibers etc provided from cloths and laundry.
In spite of the fact that the fibers are comprised as a cost effective portion of the municipal effluents, those fibers are traditionally wasted, i.e., burned, digested, disposed or disposed as an effluent towards the sea, or the rivers, causing environment problems else ware. Moreover, today, sewage sludge is massively concealed in the ground and hence regarded as one a main environmental problem. So far no one has recycled or produced organic fibers from these sources.
Few attempts for treating fibers (especially paper and paper products) have been made. Hence, US patent application 2003/0141225 to Liddle et al. discloses a method and system for separating and sorting recyclable materials from mixed waste streams. This system comprising a low surface current bath adapted to separate materials having differential wet densities. U.S. Pat. No. 3,670,968 to Galeano discloses a system and process for recovering the cellulosic fibrous material containing municipal refuse, and converting it into reusable pulp. Nevertheless, a cost-effective industrial-oriented recycling process of sewage sludge's fibers thus meets a long felt need and focuses to target environmental acute problems.